Devices and methods for occluding abnormal openings in a patient&#39;s vasculature

ABSTRACT

A medical device is provided in which one or both ends of the device encourage the formation of tissue across substantially the entire area of the respective end that is exposed to the blood flow for reducing the risk of a thrombotic embolism. The medical device includes a tubular structure having at least one expanded volume portion and a tapered transition portion. The tubular structure may be made through the braiding of a number of strands, and a first end feature may be used to secure the proximal strand ends. The proximal strand ends may be secured via the proximal end of the first end feature, such that the tapered transition portion is formed over the circumferential surface of the first end feature, and only a proximal end surface (or a portion of the proximal end surface) of the first end feature is exposed to the path of flowing blood.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. patent applicationSer. No. 13/300,322, published as US Publication No. 2013-0131717, filedon Nov. 18, 2011, which is hereby incorporated by reference in itsentirety.

BACKGROUND

1. Field of the Invention

Embodiments of the present invention relate generally to medical devicesfor treating certain vascular abnormalities. In particular, embodimentsare directed to medical devices and methods for occluding vascularabnormalities in which an end of the medical device is in the path ofblood flow, such as closure of the Left Atrial Appendage (LAA), Atrialand Ventricular Septal Defects (ASD, VSD), and Patent Ductus Arteriosus(PDA) and the like.

2. Description of the Related Art

A wide variety of intravascular devices are used in various medicalprocedures. Certain intravascular devices, such as catheters andguidewires, are generally used simply to deliver fluids or other medicaldevices to specific locations within a patient's body, such as aselective site within the vascular system. Other, frequently morecomplex, devices are used in treating specific conditions, such asdevices used in removing vascular occlusions or for treating septaldefects and the like.

In certain circumstances, it may be necessary to occlude an abnormalopening in a patient's vessel, such as an abnormal opening betweenchambers of the heart, a channel, a hole, a cavity, or the like, so asto stop blood flow therethrough. For example, atrial fibrillation mayresult in the formation of a blood clot in the left atrial appendage(LAA), which may become dislodged and enter the blood stream. Byoccluding the LAA, the release of blood clots from the LAA may besignificantly reduced, if not eliminated. Various techniques have beendeveloped to occlude the LAA. For instance, balloon-like devices havebeen developed that are configured to be implanted completely within thecavity of the LAA, while surgical techniques have also been developedwhere the cavity of the LAA is inverted and surgically closed.

Despite these techniques, it would be advantageous to provide animproved occlusion device that offers an improved surface configurationto enhance tissue coverage or tissue in-growth, particularly on surfacesadjacent flowing blood, as well as increased flexibility, improvedretention, improved thrombogenicity, and easier deployment andretrieval, thereby overcoming the shortcomings of conventional solutionsfor occluding abnormal openings within a patient's vasculature.

SUMMARY OF THE INVENTION

Embodiments therefore provide a medical device for occluding abnormalopenings in a patient's vasculature. In general, the medical device isconfigured such that an end feature of the device is recessed within atapered transition portion formed at a respective end of the medicaldevice. In this way, only an end surface of the end feature (e.g., aproximal end surface of the end feature at the proximal end of themedical device), or a portion of this surface, is exposed to the flow ofblood through the body lumen, and tissue in-growth over the end of thedevice may be enhanced and facilitated.

In one embodiment, a device is provided that is configured toself-expand from a contracted state when constrained within a deliverydevice toward an expanded state when deployed from the delivery devicefor delivery to a target site within the body lumen. The medical devicemay include a tubular structure and a first end feature. The tubularstructure may comprise a plurality of braided strands, with each braidedstrand comprising a proximal strand end and a distal strand end. Thefirst end feature may define a proximal end and a distal end, and thefirst end feature may be configured to receive and secure the proximalstrand ends via the proximal end of the first end feature. The tubularstructure may comprise an expanded volume portion proximate to the firstend feature and a tapered transition portion extending between theexpanded volume portion and the proximal end of the first end feature.In the expanded state, the expanded volume portion of the tubularstructure may define an expanded volume diameter. Moreover, in theexpanded state, the tapered transition portion may define a firsttransition diameter proximate the expanded volume portion and a secondtransition diameter proximate the proximal end of the first end feature.The first transition diameter may be greater than the second transitiondiameter, smaller than the expanded volume diameter, and disposedbetween the second transition diameter and the expanded volume diameter.In addition, the second transition diameter may be substantially equalto a diameter of the first end feature. In some cases, the secondtransition diameter may be sized to facilitate tissue growth over aproximal end of the medical device.

Embodiments of the medical device may also include a second end featureconfigured to receive and secure the distal strand ends of the pluralityof braided strands. The medical device may define a central axisextending between the first end feature and the second end feature, andthe expanded volume portion may define at least one surface that issubstantially perpendicular to the central axis. In some cases, theexpanded volume portion may define two surfaces that are substantiallyperpendicular to the central axis. The second end feature may define aproximal end and a distal end, and the second end feature may beconfigured to receive and secure the distal strand ends via the distalend of the second end feature.

In some cases, the expanded volume portion may be a first expandedvolume portion and the tapered transition portion may be a first taperedtransition portion. The tubular structure may further include a secondexpanded volume portion displaced from the first expanded volume portionand proximate the second end feature and a second tapered transitionportion extending between the second expanded volume portion and thedistal end of the second end feature. The expanded volume portion may bedisk shaped.

The expanded volume portion may be a first expanded volume portion, andthe tubular structure may further comprise a second expanded volumeportion proximate the second end feature. The first expanded volumeportion may be disk shaped, and the second expanded volume portion maybe cylindrically shaped. The first expanded volume portion and thesecond expanded volume portion may be connected by a flexible connectorsuch that the first and second expanded volume portions can articulatewith respect to each other.

The second expanded volume portion may, in some cases, comprise a coneshaped end surface affixed to the connector. In addition, a plurality ofhooks may be disposed on and may extend radially and axially outwardfrom the second expansion volume portion. The hooks may be configured toengage body tissue when the device is moved along a central axis of themedical device in a proximal direction.

At least one of the first and second expanded volume portions maycomprise a polymer fabric disposed therein, and at least a portion ofthe polymer fabric may extend substantially perpendicularly to the axis.The polymer fabric may be secured to a respective one of the first andsecond expanded volume portions.

In some embodiments, the medical device may define a proximal end and adistal end, and the proximal end of the first end feature maysubstantially coincide with the proximal end of the medical device. Themedical device may be configured to occlude a vessel, cavity, hole,septal defect, or lumen in a body. For example, the medical device maybe configured to occlude the left atrial appendage of the heart and toprevent thrombus from escaping therefrom.

In some cases, the tubular structure may be a first tubular structure,and the medical device may further comprise a second tubular structurecomprising a second plurality of braided strands. The second pluralityof braided strands may be comprised of a metal or polymer. The braidedstrands may comprise a metal having elastic properties, and/or thebraided strands may comprise a shape memory alloy. The expanded volumeportion may be heatset in a mold to memorize its expanded state.

The medical device may further comprise a polymer fabric disposed withinthe expanded volume portion, and the polymer fabric may be polyester.

In other embodiments, a medical device may be provided that isconfigured to self-expand from a contracted state when constrainedwithin a delivery device toward an expanded state when deployed from thedelivery device for delivery to a target site within the body lumen. Themedical device may comprise a tubular structure and a first end feature.The tubular structure may comprise a plurality of braided strands, andeach braided strand may comprise a proximal strand end and a distalstrand end. The first end feature may have a proximal end and a distalend, and the first end feature may be configured to receive and securethe proximal strand ends via the proximal end of the first end feature.Moreover, the proximal end of the first end feature may comprise aproximal end surface, a distal end surface, and a circumferentialsurface extending between the proximal and distal end surfaces. Thetubular structure may comprise an expanded volume portion proximate tothe first end feature and a tapered transition portion extending betweenthe expanded volume portion and the proximal end of the first endfeature. In the expanded state, the proximal strand ends may be securedto the first end feature such that the transition portion substantiallysurrounds the circumferential surface of the first end feature and onlythe proximal end surface of the first end feature or a portion of theproximal end surface is exposed to fluid flow through the body lumen.

In still other embodiments, a medical device may be provided that isconfigured to self-expand from a contracted state when constrainedwithin a delivery device toward an expanded state when deployed from thedelivery device for delivery to a target site within the body lumen. Themedical device may include a tubular structure comprising a plurality ofbraided strands, and each braided strand may comprise a proximal strandend and a distal strand end. The medical device may further include afirst end feature having a proximal end and a distal end, where thefirst end feature is configured to receive and secure the proximalstrand ends via the proximal end of the first end feature. The tubularstructure may comprise an expanded volume portion proximate to the firstend feature and a tapered transition portion extending between theexpanded volume portion and the proximal end of the first end feature.In the expanded state, the proximal strand ends may be secured to thefirst end feature such that the proximal strand ends are at leastpartially inverted at the proximal end of the first end feature.

In still other embodiments, a method of making a medical device forplacement in a body lumen is provided. The method includes braiding aplurality of strands defining proximal strand ends to form a tubularstructure and attaching a first end feature defining a proximal end anda distal end to the proximal strand ends via the proximal end of thefirst end feature. The medical device may be configured to self-expandfrom a contracted state when constrained within a delivery device towardan expanded state when deployed from the delivery device for delivery toa target site within the body lumen. The tubular structure may comprisean expanded volume portion proximate to the first end feature and atapered transition portion extending between the expanded volume portionand the proximal end of the first end feature. In the expanded state,the expanded volume portion of the tubular structure may define anexpanded volume diameter. Furthermore, in the expanded state, thetapered transition portion may define a first transition diameterproximate the expanded volume portion and a second transition diameterproximate the proximal end of the first end feature. The firsttransition diameter may be greater than the second transition diameter,smaller than the expanded volume diameter, and disposed between thesecond transition diameter and the expanded volume diameter. The secondtransition diameter may be substantially equal to a diameter of thefirst end feature.

In still other embodiments, a method of delivering a medical device isprovided. The method includes providing a medical device configured toself-expand from a contracted state when constrained within a deliverydevice toward an expanded state when deployed from the delivery devicefor delivery to a target site within the body lumen, where the medicaldevice is configured as described above. The medical device may beadvanced through a body lumen toward the target site and deployed at thetarget site.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features and advantages of embodiments of the inventionwill become apparent to those skilled in the art from the followingdetailed description of a preferred embodiment, especially whenconsidered in conjunction with the accompanying drawings in which likenumerals in the several views refer to corresponding parts.

FIG. 1 illustrates a conventional medical device that includesprotruding end clamps;

FIG. 2 is a schematic side view of a medical device in an expanded stateaccording to an exemplary embodiment;

FIG. 3 illustrates tissue growth over the proximal end of an implantedmedical device according to an exemplary embodiment;

FIG. 4 is a schematic perspective view of the medical device of FIG. 2in an expanded state from the proximal end according to an exemplaryembodiment;

FIG. 5 is a schematic side view of the medical device of FIG. 2 in acontracted state according to an exemplary embodiment;

FIG. 6 is a simplified cross-sectional view of the medical device ofFIG. 2 according to an exemplary embodiment;

FIG. 7 is a cross-sectional view of the medical device of FIG. 2according to an exemplary embodiment;

FIG. 8 is a close-up cross-sectional view of a first end feature of themedical device according to an exemplary embodiment;

FIG. 9 illustrates a medical device that includes a polymer fabric ineach of the first and second expanded volume portions according to anexemplary embodiment;

FIG. 10 is a simplified cross-sectional view of the medical device ofFIG. 6 in exploded form according to an exemplary embodiment;

FIG. 10A is a perspective cross-sectional view of the first end featureof the medical device of FIG. 10 according to an exemplary embodiment;

FIG. 11 illustrates the proximal end of a medical device according to anexemplary embodiment;

FIG. 12 illustrates the distal end of a medical device according to anexemplary embodiment;

FIG. 13 is a schematic illustration of a medical device including firstand second tubular structures (an inner and an outer layer) according toan exemplary embodiment;

FIG. 14 illustrates a flowchart for a method for making a medical devicefor occluding an abnormal opening in the body lumen;

FIG. 15A is a schematic illustration of a delivery device in a firstposition according to an exemplary embodiment;

FIG. 15B is a schematic illustration of a delivery device in a secondposition according to an exemplary embodiment;

FIG. 16 is a schematic illustration of the delivery device of FIGS. 15Aand 15B showing the guide member disposed within the lumen of a deliverycatheter;

FIG. 17 is a schematic illustration of the delivery device of FIG. 15Aengaged to the proximal end of the medical device according to anexemplary embodiment; and

FIG. 18 illustrates a flowchart for a method for delivering a medicaldevice.

DETAILED DESCRIPTION

Embodiments of the present invention now will be described more fullyhereinafter with reference to the accompanying drawings, in which some,but not all embodiments of the invention are shown. Indeed, theinvention may be embodied in many different forms and should not beconstrued as limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will satisfy applicablelegal requirements. Like numbers refer to like elements throughout.

In general, embodiments of a medical device are described that providean end feature that is recessed within a tapered transition portionformed at a respective end of the medical device, such that the endfeature does not protrude from the respective end of the device. In thisway, the medical device may be safely and easily deployed at targetsites in certain locations of the patient's vasculature where blood flowmay occur across one or both ends by providing a surface configurationthat facilitates tissue coverage while reducing the risk of a thromboticembolism. For example, in conventional devices, such as the device 10shown in FIG. 1, an end clamp 20 may be provided at a proximal end ofthe medical device that protrudes outwardly from the braided structure30. As a result, blood flow in the direction of the arrow 40 may bedisrupted in the area of the end clamp 20. Because of the smooth surfaceof the clamp and its location in the stream of blood flow, tissue growthon the clamp may not occur as quickly as it occurs over other surfacesof the device. There is always a risk of clot formation over devicesurfaces prior to tissue incorporation, so anti-clotting medications maybe prescribed to protect the patient during a period of time untiltissue coverage is complete. Embolisms may form and dislodge fromuncovered surfaces and may travel through the patient's vasculature,putting the patient at risk, so it is preferable to have device surfaceswhere tissue coverage is facilitated. Further examples of medicaldevices are provided in U.S. Publication No. US 2009/0171386 titled“Percutaneous Cather Directed Intravascular Occlusion Devices” and filedon Dec. 28, 2007, which is incorporated by reference herein in itsentirety.

Accordingly, embodiments of the medical device 100, such as shown inFIG. 2, are configured such that one or both ends 110, 120 of the deviceencourage formation of tissue across substantially the entire area ofthe respective end that is exposed to the blood flow, such that the riskof a thrombotic embolism may be minimized. An illustration of a devicethat has been placed in the body lumen at a target site for a period oftime, showing the growth of tissue 50 over at least the proximal end 110of the device, is provided in FIG. 3. Moreover, embodiments of thepresent invention provide for attachment of the end feature(s) in such away that radial expansion and contraction of the medical device as themedical device is moved between contracted and expanded states isfacilitated as compared to conventional devices, as described in greaterdetail below.

It is understood that the use of the term “target site” is not meant tobe limiting, as the medical device may be configured to treat any targetsite, such as an abnormality, a vessel, an organ, an opening, a chamber,a channel, a hole, a cavity, or the like, located anywhere in the body.The term “vascular abnormality,” as used herein is not meant to belimiting, as the medical device may be configured to bridge or otherwisesupport a variety of vascular abnormalities. For example, the vascularabnormality could be any abnormality that affects the shape of thenative lumen, such as an LAA, an atrial septal defect, a lesion, avessel dissection, or a tumor. Embodiments of the medical device may beuseful, for example, for occluding an LAA, ASD, VSD, or PDA, as notedabove. Furthermore, the term “lumen” is also not meant to be limiting,as the vascular abnormality may reside in a variety of locations withinthe vasculature, such as a vessel, an artery, a vein, a passageway, anorgan, a cavity, or the like. For ease of explanation, the examples usedherein refer to the occlusion of an LAA. As used herein, the term“proximal” refers to a part of the medical device or the delivery devicethat is closest to the operator, and the term “distal” refers to a partof the medical device or the delivery device that is farther from theoperator at any given time as the medical device is being deliveredthrough the delivery device.

According to one embodiment of the present invention for forming themedical device 100, a plurality of strands may be braided together toform a tubular structure. Although the strands are described as beingbraided, it is understood that according to additional embodiments ofthe present invention, the medical device 100 may be formed by braiding,interweaving, knitting, or otherwise combining filamentary materialstogether, such as by using a conventional braiding machine. Thesefilamentary materials may include, for example, fibers, thread, yarn,cable, metallic wires, polymer monofilament or multifilament strands,and combinations of these materials, any of which are referenced hereinas “strands,” and such terms may be used interchangeably. The strandsmay be comprised of any material, such as natural materials, polymers,metals, metallic alloys, or combinations of the same. The strands may bebraided to have a predetermined pick and pitch to define openings orfenestrations so as to vary the impedance of blood flow therethrough.

In some cases, other techniques may be used to form the tubularstructure. For example, the tubular structure could be etched or lasercut from a tube such as to form an interstice geometry, or the tubularstructure could comprise an occlusion material coupled to a scaffoldingstructure or a plurality of slices of a tubular member coupled together,such as via gluing. Moreover, it is understood that the medical device100 may comprise one or more layers of occluding material such that themedical device may include a variety of occluding materials capable ofat least partially inhibiting blood flow therethrough in order tofacilitate the formation of thrombus.

According to one embodiment, the occluding material of the tubularstructure 130, shown in FIG. 4, is a metal fabric including a pluralityof strands 135, such as two sets of essentially parallel generallyhelical strands, with the strands of one set having a “hand,” or adirection of rotation, opposite that of the other set.

The pitch of the strands 135 (the angle defined between the turns of thestrands and the axis of the braid) and the pick of the fabric (thenumber of wire strand crossovers per unit length) may be adjusted asdesired for a particular application. The wire strands of the metalfabric used in one embodiment of the present method may be formed of amaterial that is both resilient and can be heat treated to substantiallyset a desired shape. Materials which may be suitable for this purposeinclude a cobalt-based low thermal expansion alloy referred to in thefield as Elgiloy, nickel-based high temperature high-strength“superalloys” commercially available from Haynes International under thetrade name Hastelloy, nickel-based heat treatable alloys sold under thename Incoloy by International Nickel, and a number of different gradesof stainless steel. An important consideration in choosing a suitablematerial for the wires strands is that the wires retain a suitableamount of the deformation induced by the molding surface (as describedbelow) when subjected to a predetermined heat treatment and elasticallyreturn to said molded shape after substantial deformation.

One class of materials which meets these qualifications is so-calledshape memory alloys. One particular shape memory alloy that may be usedis Nitinol. Nitinol alloys are also highly elastic and are said to be“superelastic,” or “pseudoelastic.” This elasticity may allow the deviceto return to a preset expanded configuration for deployment followingpassage in a distorted form through a delivery catheter. Moreover, othersuitable materials include those that are compatible with magneticresonance imaging (MRI), as some materials may cause heat or torqueresulting from performing MRI, and some materials may distort the MRIimage. Thus, metallic and/or non-metallic materials that reduce oreliminate these potential problems resulting from using MRI may beemployed. Further examples of materials and manufacturing methods formedical devices with shape memory properties are provided in U.S.Publication No. 2007/0265656 titled “Multi-layer Braided Structures forOccluding Vascular Defects” and filed on Jun. 21, 2007, which isincorporated by reference herein in its entirety.

In some embodiments, one or more layers of fabric may be employed toform a medical device, as described in greater detail below. Forexample, two layers of metal fabric could be separately woven intotubular structures, with one tubular structure coaxially disposed withinthe second tubular structure. For further discussion regarding amulti-layer braided device and techniques for fabricating such a device,see U.S. Patent Appl. Publ. No. 2007/0168019 to Amplatz et al., which ishereby incorporated in its entirety by reference.

The tubular structure 130 used to fabricate medical devices 100according to one embodiment of the present invention may use wirestrands ranging in diameter from 0.0015 in. to 0.005 in., preferably inthe range of 0.003 to 0.0045 in. The number of wires in the tubularbraid may vary from 36 to 144 but preferably is in the range of 72 to144. The pick count of the braid may vary from 30 to 100. The fabric maythus have an average area between supporting fibers of betweenapproximately 0.0016 sq. cm. and 0.25 sq. cm.

Once an appropriately sized tubular structure is obtained, the fabricmay be deformed to generally conform to a surface of a molding element.For example, the tubular structure 130 may be deformed to define one ormore expanded volume portions 180, 185, as shown in FIG. 4. Deformingthe fabric will reorient the relative positions of the wire strands ofthe metal fabric from their initial order to a second, reorientedconfiguration. The shape of the molding element should be selected todeform the fabric into substantially the shape of the desired medicaldevice when unconstrained. Once the molding element is assembled withthe metal fabric generally conforming to a molding surface of thatelement, the fabric can be subjected to a heat treatment while itremains in contact with that molding surface. After the heat treatment,the fabric may be removed from contact with the molding element andshould substantially retain its shape in a deformed state.

In this way, a medical device 100 may be formed that is configured toself-expand from a contracted state when constrained within a deliverydevice (such as a catheter, represented by dashed lines in FIG. 5)toward an expanded state when deployed from the delivery device fordelivery to a target site within the body lumen (shown in FIG. 2). Inthe contracted state, the medical device 100 may define a length L_(e),and in the expanded state the medical device may define a length L_(e).The medical device 100 may be moved to the contracted state, forexample, when the ends 110, 120 of the device are pulled away from eachother and/or a radial constraint is applied to the device. In otherwords, as shown in FIG. 5, the application of a tensile force F on theends of the device 100 may serve to collapse the overall outer diameterD_(e) of the device such that it may achieve a reduced diameter D_(c),allowing the device to be received within a lumen of a delivery devicein the contracted state (FIG. 5) for delivery to the target site. Thus,in this example, the delivery device (e.g., a catheter) applies theradial constraint to maintain the medical device 100 in the contractedstate.

The medical device 100 may be configured, however, such that, when theradial constraint is removed, the device can self-expand to the expandedstate shown in FIG. 2. For example, as the medical device 100 isunsheathed from the delivery device, portions of the medical device thatare no longer constrained by the delivery device may self-expand andfreely return to the expanded state, and once the medical device hasbeen fully deployed from the delivery device proximate the target site,the medical device will at least partially assume the expanded state.For example, the vessel diameter or the diameter of the opening in whichthe medical device 100 is inserted may limit complete return to theexpanded state.

Thus, a medical device having a predetermined shape may be collapsed bylongitudinally stretching the medical device (as illustrated in FIG. 5)for inserting the device into the lumen of a delivery device (e.g., aguide catheter or delivery sheath). The delivery device may then bepositioned and advanced in a patient's body such that the distal end ofthe delivery device is adjacent to the target site (e.g., straddling theabnormal opening). The medical device 100 may be advanced through thedelivery device such that the distal end of the medical device is nearthe distal end of the delivery device. Thus, as the medical device isdeployed from the distal end of the delivery device, the diameter of themedical device is allowed to self-expand at the target site, e.g., toocclude the abnormal opening in the patient's vasculature.

A simplified cross-section of one embodiment of the medical device isshown in FIG. 6, with a more detailed cross-section depicting thebraided strands from which the tubular structure is formed shown in FIG.7. A simplified exploded view of the medical device 100 is shown in FIG.10. With reference to FIGS. 4, 6, 7, and 10, embodiments of the medicaldevice 100 comprise a tubular structure 130 comprising a plurality ofbraided strands 135 including proximal strand ends 137. A first endfeature 140 is provided that includes a proximal end 142 and a distalend 144. The first end feature 140 may be configured to receive andsecure the proximal strand ends 137 via the proximal end of the firstend feature. In some cases, as shown in FIGS. 8 and 10, the first endfeature 140 may include an inner bushing 160 (e.g., a stainless steelbushing) in which an inner lumen 162 is formed, and internal threads 164may be defined on an inner surface of the threaded inner bushing 160 forreceiving corresponding threads of a pusher wire of a delivery system,for example. The plurality of strands 135 may be placed around thethreaded inner bushing 160, as shown, and another, larger diameter outerbushing 170 (e.g., a platinum/iridium alloy bushing) may be disposedaround the inner bushing 160, such that the proximal ends 137 of thebraided strands 135 are secured (e.g., tightly wedged) between the innerand outer bushings 160, 170. The proximal ends 137 of the braidedstrands 135 may then be secured, e.g., by laser welding such that a weld165 is created to fuse both the inner and outer bushings 160, 170 to thestrands 135. The braid may then be inverted (e.g., by reversing thebraiding direction) so that when the medical device 100 is formed, thefirst end feature 140 is recessed from the proximal end 110 of thedevice, as shown, and is internal to the medical device.

With reference to FIG. 10, the first end feature 140 may comprise amarker band 172 on an external surface of the outer bushing 170 that isconfigured to facilitate placement of the medical device 100 at thetarget site. For example, the marker band 172 may include a radiopaquematerial, such as a platinum iridium alloy, to allow a medicalpractitioner to view the location of the medical device 100 (and, moreparticularly, the location of the proximal end 110 of the medicaldevice) within the body using radio fluoroscopy to facilitate properdelivery and positioning of the device. In some cases, however, theouter bushing 170 itself is made of a radiopaque material, such that thebushing serves as the marker band.

Referring again to FIGS. 4, 6, 7, and 10, the tubular structure 130 maycomprise an expanded volume portion 180 proximate the first end featureand a tapered transition portion 190 extending between the expandedvolume portion 180 and the proximal end 142 of the first end feature140. For example, the inversion of the braid at the proximal end 142 ofthe first end feature 140 (FIG. 8) may serve to create the taperedtransition portion 190. In the expanded state (e.g., shown in FIG. 2),the expanded volume portion 180 of the tubular structure may have anexpanded volume diameter D_(e), and the tapered transition portion 190may define a first transition diameter D₁ proximate the expanded volumeportion and a second transition diameter D₂ proximate the proximal end142 of the first end feature 140. As shown, the first transitiondiameter D₁ may be greater than the second transition diameter D₂, butsmaller than the expanded volume diameter D_(e). Moreover, the firsttransition diameter D₁ may be disposed between the second transitiondiameter D₂ and the expanded volume diameter D_(e), and the secondtransition diameter D₂ may be substantially equal to a diameter of thefirst end feature 140.

The tapered transition portion 190 may be configured such that thesecond transition diameter D₂ is sized to allow tissue growth over theproximal end 110 of the medical device 100, as shown in FIG. 3. Saiddifferently, because the proximal end 142 of the first end feature 140substantially coincides with the proximal end 110 of the medical device100, the proximal end 110 of the medical device has a small smoothsurface (e.g., as compared to the protruding end clamp 20 of theconventional medical device 10 shown in FIG. 1) that allows andfacilitates rapid tissue growth over the surface to minimize the chanceof a thrombotic embolus being released from the device. For example, asshown in FIG. 10A, the first end feature 140 may include a proximal endsurface 145, a distal end surface (not visible), and a circumferentialsurface 146 extending between the proximal and distal surfaces. Becauseof the way the proximal strand ends are secured to the first end feature(as depicted in the figures), the transition portion 190 substantiallysurrounds the circumferential surface, such that only the proximal endsurface (or a portion of the proximal end surface) of the first endfeature 140 is exposed to fluid flow through the body lumen.

With reference to FIGS. 6 and 7, the medical device 100 may furthercomprise a second end feature 150 that is configured to receive andsecure distal strand ends 138 (FIG. 6) of the plurality of braidedstrands. The second end feature 150 may, for example, define a proximalend 152 and a distal end 154, and the proximal end 152 of the second endfeature 150 may define an opening at least partially therethrough. Theopening at the proximal end 152 of the second feature 150 may beconfigured to receive the distal strand ends 138 and may secure themtogether and/or to the second end feature 150. For example, the secondend feature 150 may be configured to hold the distal strand endstogether 138 by clamping, welding, soldering, brazing, or otherwiseadhering them to each other and/or to the second end feature 150. Thesecond end feature 150 may also include a marker band 173 (FIG. 10) tohelp locate the distal end 120 of the medical device 100, as noted abovewith respect to the first end feature 140. Views of the proximal anddistal ends 110, 120 of the medical device are shown in FIGS. 11 and 12.

In some embodiments, however, not shown, the second end feature 150 maybe configured similarly to the first end feature 140, in that the secondend feature 150 may be configured to receive and secure the distalstrand ends 138 via the distal end 154 of the second end feature. Thus,the distal end 154 of the second end feature 150 may substantiallycoincide with the distal end 120 of the medical device 100, which mayallow tissue to grow over the surface of the distal end 120 withoutcreating thrombus as noted above with respect to the first end feature140. Such a configuration for both the first and second end features140, 150 may be especially useful in cases in which both the proximaland distal ends 110, 120 of the medical device 100 are to be exposed totransverse blood flow.

The medical device 100 may have various configurations depending onfactors such as the type of abnormality to be occluded, the location ofthe target site, the condition of the patient's vasculature, and thepractitioner's preferences. For example, in the depicted embodiment ofFIG. 7, the medical device 100 has an expanded volume portion 180proximate the first end feature that defines at least one surface (inthis case, two surfaces 182, 184) that are substantially perpendicularto a central axis A extending between the first end feature 140 and thesecond end feature 150. Moreover, the expanded volume portion 180 may bea first expanded volume portion, and a second expanded volume portion185 may be provided proximate the second end feature 150 that isdisplaced axially from the first expanded volume portion 180. In somecases, as noted above, the tapered transition portion 190 may be a firsttransition portion, and a second transition portion may be defined thatextends between the second expanded volume portion 185 and the secondend feature 150 (not shown).

As depicted in FIG. 7, the expanded volume portion 180 may be generallydisk shaped, for example, to facilitate maintaining the medical device100 in position at the target site, as described in greater detailbelow. The second expanded volume portion 185 may, in some cases, be agenerally cylindrically shaped portion that is axially disposed towardthe second end feature 150 (e.g., distally from the first end feature140 and/or the first expanded volume portion 180). In some cases, thesecond expanded volume portion 185 may be sized to be somewhat larger indiameter (e.g., about 10-30%), than the inside diameter of the vessel,cavity, or lumen to be occluded. This sizing may be intended tofacilitate anchoring the device to prevent dislodgement.

At the same time, the first expanded volume portion 180 of the device100 may have a diameter that is intended to abut the adjacent wallsurrounding the abnormal aperture to prevent device movement toward thesecond expanded volume portion 185 and to assist in sealing theaperture. For example, the first expanded volume portion 180 may beoversized so as to be capable of overlying the ostium or opening of theLAA and lying adjacent to, and in flush contact with, the wall of theatrium. The diameter of the second expanded volume portion may be lessthan the diameter of the first volume portion so as to fit in the LAA.The first expanded volume portion 180 may also be flexible so as to becapable of conforming to the curvature of the wall of the atrium in LAAapplications or other vascular structures in other applications.Although one configuration of the first and second expanded volumeportions 180, 185 is described above and shown in the figures, variousother configurations and sizes may be used depending on the particularapplication or condition to be treated. For example, one or bothexpanded volume portions 180, 185 may be flat disks or disks having aconvex distal end, or the device may include a smaller diameter centralcylindrical portion between two larger diameter disks. Moreover, thedepth or thickness of the first and/or second expanded volume portionsmay depend on the thickness and number of layers used to make themedical device 100.

In some embodiments, the tubular structure 130 may further include aflexible connecting portion 188 that extends between and connects thefirst expanded volume portion 180 and the second expanded volume portion185. The flexible connecting portion 188 may define, for example anarrower connecting diameter D₃ (FIG. 2) with respect to the diametersof the first and second expanded volume portions 180, 185, such that thefirst expanded volume portion 180 is allowed to articulate (e.g., pivot)relative to the second expanded volume portion 185. In this way, therelative positions of the first and second expanded volume portions 180,185 may be adjustable to accommodate different target sites andconfigurations (e.g., size and location) of abnormal openings to beoccluded. Furthermore, the second expanded volume portion 185 may definea conical surface 189 from which the flexible connecting portion 188extends, as shown in FIG. 7. The conical surface may allow the distancebetween the first expanded volume portion 180 and the second expandedvolume portion 185 to vary and may thus provide a way of creatingtension between the expanded volume portions and retention hooks(described below) to maintain the first expanded volume portion 180 overthe ostium and keep the device in place.

Referring now to FIGS. 2 and 4, in some embodiments, the medical device100 may include retention hooks 200. The retention hooks 200 may befabricated from Nitinol wire that is heat set into a hook shape at eachend and has a bend 205 (FIG. 2), e.g., a bend of less than about 180degrees, in the mid length segment of the wire so as to create twointerconnected hooks. The hooks 200 may also at least partially extendwithin the medical device 100 in some cases (not shown). In the depictedembodiments, the hooks 200 are disposed on the second expanded volumeportion 185, and the ends 210 of the hooks 200 extend radially out fromthe second volume portion and are oriented toward the first expandedvolume portion 180. For example, the hooks 200 may be sutured, woven,fastened, or otherwise attached to the braided fabric forming the secondexpanded volume portion 185.

According to one embodiment, the wires of the hooks 200 may be about0.003-0.007 inches in diameter and 2-10 mm in length and may be flexibleenough to be back loaded into a delivery catheter or forward loaded ifintroduced in a straightened-out configuration. The medical device 100may have any number of hooks 200, and in some cases three to twelvepairs of hooks may be provided, such as eight pairs of hooks. The hooks200 may thus be configured to assist in the retention of the medicaldevice 100 by resisting motion of the device in the vessel in adirection that would cause the hooks to engage the tissue. In otherwords, the hooks 200 are configured to engage body tissue when themedical device 100 is moved along its axis A in the proximal direction.In the depicted embodiment, the hooks 200 do not have barbs so that theengagement with the tissue is reversible by movement of the medicaldevice 100 in a distal direction. Moreover, in LAA applications, forexample, the hooks 200 may be configured to penetrate the wall of theLAA, but would not extend completely through the wall of the LAA. Thus,the hooks 200 may reduce the incidence of effusion by not puncturingthrough the wall of the LAA.

In some embodiments, the hooks 200 may be integral to the medical device100, such as when individual strands of the braided tubular structure130 are isolated, cut, and a short portion of the wire adjacent the cutformed into an outward projecting hook. Such a configuration may providefor a medical device 100 that has a significantly lower profile as noadded material (e.g., no separate hooks) contributes to the collapsedoverall diameter D_(c) (FIG. 5) of the medical device during passagethrough a delivery catheter. In addition, through the use of integralhooks 200 there are no added suture materials or suture knots that areneeded to attach the hooks to the braided tubular structure, which alsotranslates into a reduced profile of the medical device.

As noted above, the second expanded volume portion 185 may be oversizedso that it will engage the lumen of the vessel, body organ, or the liketo be occluded. The medical device 100 may then be held in place by thecombination of the radial engagement of the second expanded volumeportion 185 with the lumen of the vessel, body organ, or the like andthe engagement of the hooks 200 with the vessel wall. Over a relativelyshort period of time, thrombi will form in and on the medical device 100and occlude the lumen. Although the first and second expanded volumeportions 180, 185 may be various sizes, the first expanded volumeportion may be at least about 10% larger in diameter than the secondexpanded volume portion according to one embodiment.

For example, in the case of a medical device 100 that is implantedwithin the LAA, the medical device 100 may be positioned such that thefirst expanded volume portion 180 overlies the ostium of the LAA, whilethe second expanded volume portion 185 is positioned within the LAA.Thus, the first expanded volume portion 180 may be sized and configuredto ensure that the first expanded volume portion 180 is implanted to apredetermined depth within the LAA. The second expanded volume portion185 may in turn be sized and configured to self expand and engage thewall of the LAA, and the hooks 200 may be configured to penetrate intothe wall of the LAA, as explained below. Over time, thrombi will form inand on the first and second expanded volume portions 180, 185 to occludethe LAA.

In some embodiments, in order to speed up the occlusion of the medicaldevice 100, the medical device may be at least partially coated with asuitable thrombogenic agent, filled with a fiber (e.g., a polymerfabric), braided with an increased number of strands, or includemultiple layers of braided strands. For example, the medical device 100may include one or more layers of polymer fabric 220 positioned withinthe first and/or second expanded volume portions 180, 185, as shown inFIG. 9. In particular, one or more layers of polymer fabric 220 may besized and configured to be positioned within each of the first andsecond expanded volume portions 180, 185, such that the polymer fabricextends substantially perpendicularly to the axis A of the medicaldevice 100. Each piece of polymer fabric 220 may be suturedcircumferentially about its periphery and about the inner circumferenceof the first and second expanded volume portions 180, 185, respectively.The polymer fabric 220 may be flexible and may be easily collapsed withthe medical device 100 for delivery through a catheter. In this way, theinterwoven fiber (which in some embodiments may be polyester) may attachto a clot to retain the clot firmly within the device as it forms theocclusion.

Although the embodiments depicted in FIGS. 2-12 show a medical devicehaving a single layer of braided fabric (e.g., a single tubularstructure 130), in some cases a second plurality of strands may bebraided to form a second tubular structure, such that medical deviceincludes an inner and outer layer. Referring FIG. 13, for example, themedical device 100 may include an inner layer 250 and an outer layer260. The inner layer 250 may be disposed adjacent to the outer layer260, and in some cases the inner layer may have a different shape thanthe outer layer. The first and second expanded volume portions 180, 185and the connecting portion 188 may be integrally formed from the sametubular structure.

In some embodiments, the pick count, or the number of strand crossingsper unit length of the layers 250, 260, may be set at the same ordifferent predetermined values. For example, the inner layer 250 maydefine a first pick count, and the outer layer 260 may define a secondpick count, where the second pick count is different from the first pickcount. Although the first pick count, as braided, may be different fromthe second pick count, as braided, the first and second pick counts maybe selected such that the relationship between the reduction in diameterand the elongation of the inner layer 250 is substantially the same asthe relationship between the reduction in diameter and the elongation ofthe outer layer 260 as the medical device 100 is moved between theexpanded and contracted states. For example, a ratio of the decrease indiameter of the inner layer 250 to the increase in length of the innerlayer 250 may be substantially the same as a ratio of the decrease indiameter of the outer layer 260 to the increase in length of the outerlayer 260. Thus, adjacent portions of the inner and outer layers 250,260 may remain in their relative adjacent positions as the medicaldevice 100 is moved between the expanded and contracted states. In thisway, the inner layer 250 and the outer layer 260 of the medical device100 may cooperatively collapse and expand at generally the same rate,which enhances the stability of the medical device and facilitates itsdelivery into the vessel lumen and subsequent self-expansion. In thecase where the inner and outer layers have different shapes from oneanother, the pick count of each layer may be selected such that in theelongated, contracted state each layer is substantially the same length.

Furthermore, the helix angle of the strands (e.g., the angle formedbetween the strand and the longitudinal axis of the braid mandrel as thestrand is applied to the mandrel) used to braid the plurality of strandsof the inner and outer layers 250, 260 may be the same or different. Thehelix angles may be selected such that the plurality of strands of theinner layer 250 is braided at a first helix angle, and the plurality ofstrands of the outer layer 260 is braided at a second helix angle toensure that the relationship between the reduction in diameter and theelongation of the inner layer is substantially the same as therelationship between the reduction in diameter and the elongation of theouter layer as the at least one layer is moved between the expandedstate and the contracted state. In the case where the inner and outerlayers have different shapes from one another, the helix angle of eachlayer may be selected such that in the elongated, contracted state eachlayer is substantially the same length.

As noted above, the uniform movement that results between the inner andouter layers 250, 260 may thus reduce the risk of bunching or gatheringof the layers within the medical device 100, which would otherwisereduce the effectiveness of the medical device by increasing itsdelivery profile and/or generating gaps between the various layers ofmaterial that may cause leaks.

The plurality of strands forming the second tubular structure may bemade of the same or different material as the strands forming the firsttubular structure, described above. Thus, the strands of the secondtubular structure may be comprised of metal or polymer material. Forexample the second tubular structure may be made of stainless steel,other metallic alloys, highly elastic alloys, and/or shape memoryalloys, which are both resilient and can be heat treated tosubstantially set a desired shape, as noted above with respect to thefirst tubular structure. In addition, polymeric materials may becombined with other materials in the formation of tubular structures forcertain applications. For example, the medical device 100 may include acombination of polyester strands and stainless steel wire. Thus, in someembodiments, the plurality of braided strands of the inner layer 250 mayinclude Nitinol, and the plurality of braided strands of the outer layer260 may include a polymer, or vice versa.

A method for making a medical device for placement in a body lumen asdescribed above is summarized in FIG. 14. The method includes braiding aplurality of strands defining proximal strand ends to form a tubularstructure at Block 300 and attaching a first end feature defining aproximal end and a distal end to the proximal strand ends via theproximal end of the first end feature at Block 310. As described abovewith reference to the figures, the tubular structure may define a moldedand heat set resilient expanded volume portion proximate to the firstend feature and a tapered transition portion extending between theexpanded volume portion and the proximal end of the first end feature.In the expanded state, the expanded volume portion of the tubularstructure may define an expanded volume diameter, and the taperedtransition portion may define a first transition diameter proximate theexpanded volume portion and a second transition diameter proximate theproximal end of the first end feature. As described above andillustrated in the referenced figures, the first transition diameter maybe greater than the second transition diameter, smaller than theexpanded volume diameter, and disposed between the second transitiondiameter and the expanded volume diameter. The second transitiondiameter may be substantially equal to a diameter of the first endfeature. In this way, the first end feature may be substantiallysurrounded by the tapered transition portion, such that the proximal endof the first end feature substantially coincides with the proximal endof the medical device.

As noted above, a second end feature defining a proximal end and adistal end may be attached to the distal strand ends. Block 320. In somecases, the second end feature may receive the distal strand ends via theproximal end of the second feature, as shown in the figures, whereas inother cases the second end feature may receive the distal strand endsvia the distal end of the second end feature similar to the first endfeature, thereby also keeping the second end feature from protrudingfrom the distal end of the medical device. The medical device may bemodified and configured in various other ways, such as by attachingretention hooks to the tubular structure (e.g., to the outside of secondexpanded volume portion) (Block 330), including a polymer fabric in oneor more of the expanded volume portions (Block 340), and/or coating thedevice with a thrombogenic agent (Block 350), as described in greaterdetail above.

Referring now to FIGS. 15A, 15B, 16, and 17, a delivery device 400 maybe provided for deploying embodiments of the medical device 100described above. The delivery device 400 may include an inner pusherwire 410 with a distal end 415 defining external threads. The externalthreads of the pusher wire 410 may be configured to engage correspondinginternal threads 164 of the first end feature 140 (shown in FIG. 8) soas to releasably attach the medical device 100 to the delivery device400 for delivery to and deployment at the target site, as illustrated inFIG. 17.

The delivery device 400 may further include an outer member 420 defininga lumen through which the inner pusher wire 410 is slideably received.In other words, the inner pusher wire 410 may be axially moveable withinthe outer member 420, such that the inner pusher wire may be movedbetween the position shown in FIG. 15A and FIG. 15B, for example. Adistal end of the outer member 420 may include a guide member 430configured to guide the proximal end 110 of the medical device into adistal end of a delivery sheath 440. In some cases, the guide member 430may be made of a polymer material. The guide member 430 may have atapered external surface, such that the diameter D_(d) of the guidemember at its distal end is approximately the same as (e.g., slightlyless than) the inner diameter of the delivery sheath 440 and thediameter D_(p) of the guide member at its proximal end is approximatelythe same as (e.g., slightly greater than) the outer diameter of theouter member 420. Moreover, as shown in FIG. 17, the distal diameterD_(d) of the guide member may approximate the second transition diameterD₂ of the transition portion 190, such that the taper of the transitionportion 190 and the guide member generally correspond to one another. Insome cases, as shown, the outer surface of the guide member 430 mayinclude grooves or concavities 431, which may serve to prevent the taperof the guide member from acting as a plunger that draws air into thedelivery sheath 440 from the proximal end as the medical device 100 isadvanced to toward the distal end 445. In other words, the concavities431 may allow fluid to flow through the delivery sheath 440, such that apositive blood pressure exists in the delivery sheath with respect tothe pressure outside the body.

The function of the guide member 430 may be illustrated by the followingexample. When accessing a tortuous path (e.g., a vessel that includesone or more small radius curves), the pusher wire 410 and/or the outermember 420 may be biased to one side of the delivery sheath 440 once themedical device 100 has been deployed (e.g., is outside the deliverysheath 440, but still attached to the pusher wire 410). In some cases,the medical device 100 must be recaptured within the delivery sheath440, for example, to reposition the medical device at the target site orto replace the device for one of a different size. As the medical device100 is moved proximally (closer) to the distal end 445 of the deliverysheath 440 during recapture, the medical device 100 may not be axiallyaligned with the lumen of the delivery sheath (e.g., as a result of thecurvature of the vessel within which the delivery sheath is disposed).The guide member 430, by virtue of its tapered shape, may thus bring theproximal end 110 of the medical device 100 into closer axial alignmentwith the lumen of the delivery sheath to allow for easier recapture andto minimize the risk of damaging the medical device during recapture.

Accordingly, in FIG. 18, a method for delivering a medical device asdescribed above is summarized. The method includes providing a medicaldevice configured as described above in connection with one or more ofFIGS. 2-17. Block 500. For example, the medical device may include atubular structure comprising a plurality of braided strands definingproximal strand ends and a first end feature defining a proximal end anda distal end, where the first end feature is configured to receive andsecure the proximal strand ends via the proximal end of the first endfeature. As described above, the tubular structure may define one ormore expanded volume portions and at least one tapered transitionportion.

The method of delivery may further include advancing the medical devicethrough the body lumen toward the target site (Block 510) and deployingthe medical device at the target site (Block 520). In some cases, asdescribed above, the method may further include recapturing the medicaldevice within the delivery sheath (Block 530), repositioning a distalend of the delivery device (Block 540), and redeploying the medicaldevice (Block 550). Once the medical device is positioned at a desiredlocation, the delivery device may be disengaged from the medical device(e.g., via unthreading the medical device from the pusher wire) andwithdrawn from the body lumen, leaving the medical device in place atthe target site. Block 560.

The method depicted in FIG. 14 and described above represents only onemethod for making a medical device for placement in a body lumen.Similarly, the method depicted in FIG. 18 and described above representsonly one method for delivering a medical device. In some embodiments,certain ones of the steps described above may be modified or furtheramplified. Furthermore, in some embodiments, additional optional stepsmay be included, some examples of which are shown in dashed lines inFIGS. 14 and 18. Modifications, additions, or amplifications to thesteps above may be performed in any order and in any combination. Theparticular methods of manufacturing and delivery will depend on thedesired configuration of the medical device, the patient's anatomy, thecondition and location of the target site, the preferences of thepractitioner, and/or other considerations.

This invention has been described herein in considerable detail in orderto comply with the Patent Statutes and to provide those skilled in theart with the information needed to apply the novel principles and toconstruct and use embodiments of the example as required. However, it isto be understood that specifically different devices can carry out theinvention and that various modifications can be accomplished withoutdeparting from the scope of the invention itself. For example, optionsshown for one embodiment could easily be applied to other embodiments,as desired for a particular application, without departing from thescope of this invention.

That which is claimed:
 1. A medical device configured to self-expandfrom a contracted state toward an expanded state when deployed from adelivery device, the medical device comprising: a tubular structurecomprising a plurality of braided strands, each braided strandcomprising a proximal strand end and a distal strand end; and a firstend feature defining a proximal end and a distal end, wherein the firstend feature is configured to receive and secure the proximal strand endsvia the proximal end of the first end feature.
 2. The medical device ofclaim 1, wherein the tubular structure further comprises: a firstexpanded volume portion proximate to the first end feature; and a firsttapered transition portion extending between the first expanded volumeportion and the proximal end of the first end feature.
 3. The medicaldevice of claim 2 further comprising: a second end feature configured toreceive and secure the distal strand ends.
 4. The medical device ofclaim 3, wherein the second end feature defines a proximal end and adistal end, wherein the second end feature is configured to receive andsecure the distal strand ends via the distal end of the second endfeature.
 5. The medical device of claim 4, wherein the tubular structurefurther comprises: a second expanded volume portion displaced from thefirst expanded volume portion and proximate the second end feature; anda second tapered transition portion extending between the secondexpanded volume portion and the distal end of the second end feature. 6.The medical device of claim 5, wherein the first expanded volume portionis disk shaped, and wherein the second expanded volume portion iscylindrically shaped.
 7. The medical device of claim 6, wherein thefirst expanded volume portion and the second expanded volume portion areconnected by a flexible connector such that the first and secondexpanded volume portions articulate with respect to each other.
 8. Themedical device of claim 1, wherein the medical device defines a proximalend and a distal end, wherein the proximal end of the first end featuresubstantially coincides with the proximal end of the medical device. 9.The medical device of claim 1, wherein the medical device is configuredto occlude a vessel, cavity, hole, septal defect, or lumen in a body.10. The medical device of claim 9, wherein the medical device isconfigured to occlude the left atrial appendage of the heart and toprevent thrombus from escaping therefrom.
 11. A method of making amedical device for placement in a body lumen comprising: braiding aplurality of strands defining proximal strand ends to form a tubularstructure; and attaching a first end feature defining a proximal end anda distal end to the proximal strand ends via the proximal end of thefirst end feature.
 12. The method of claim 11, wherein attaching thefirst end feature to the proximal strand ends comprises at leastpartially inverting the proximal strand ends at the proximal end of thefirst end feature.
 13. The method of claim 12, wherein attaching thefirst end feature to the proximal strand ends comprises at leastpartially inverting the proximal strand ends between an inner bushingand an outer bushing of the first end feature.
 14. The method of claim13 further comprising fusing the inner bushing and the outer bushing tothe proximal strand ends.
 15. A medical device configured to self-expandfrom a contracted state toward an expanded state when deployed from adelivery device, the medical device comprising: a tubular structurecomprising a plurality of braided strands, each braided strandcomprising a proximal strand end and a distal strand end; and a firstend feature having a proximal end and a distal end, wherein the proximalstrand ends are secured to the first end feature such that the proximalstrand ends are at least partially inverted at the proximal end of thefirst end feature.
 16. The medical device of claim 15, wherein thetubular structure comprises an expanded volume portion proximate to thefirst end feature and a tapered transition portion extending between theexpanded volume portion and the proximal end of the first end feature.17. The medical device of claim 16, wherein the first end featurecomprises: a proximal end surface, a distal end surface, and acircumferential surface extending between the proximal and distal endsurfaces, wherein the proximal strand ends are secured to the first endfeature such that the tapered transition portion substantially surroundsthe circumferential surface of the first end feature and only theproximal end surface of the first end feature or a portion of theproximal end surface is exposed.
 18. The medical device of claim 15,wherein the first end feature comprises: an inner bushing; and an outerbushing disposed around the inner bushing, wherein the proximal strandends are secured between the inner bushing and the outer bushing. 19.The medical device of claim 18, wherein the inner bushing and the outerbushing are fused to the proximal strand ends.
 20. The medical device ofclaim 18, wherein the inner bushing comprises threads on an innersurface of the inner bushing for receiving threads of a delivery system.